Method for reducing the wet etch rate of a sin film without damaging the underlying substrate

ABSTRACT

Methods and apparatuses for forming conformal, low wet etch rate silicon nitride films having low hydrogen content using atomic layer deposition are described herein. Methods involve depositing a silicon nitride film at a first temperature using a bromine-containing and/or iodine-containing silicon precursor and nitrogen by atomic layer deposition and treating the silicon nitride film using a plasma at a temperature less than about 100° C. Methods and apparatuses are suitable for forming conformal, dense, low wet etch rate silicon nitride films as encapsulation layers over chalcogenide materials for memory applications.

BACKGROUND

Semiconductor device fabrication may involve deposition of siliconnitride films. Silicon nitride thin films have unique physical,chemical, and mechanical properties and thus are used in a variety ofapplications. For example, silicon nitride films may be used indiffusion barriers, gate insulators, sidewall spacers, encapsulationlayers, strained films in transistors, and the like. Conventionalmethods of depositing silicon nitride films may damage components of theprocess chamber where deposition is performed, or may damage substratematerials.

SUMMARY

Provided herein are methods of processing substrates. One aspectinvolves a method of processing a substrate, the method including: (a)providing the substrate to a chamber; (b) depositing a conformal siliconnitride film over the substrate at a first temperature by: (i) exposingthe substrate to a chlorine-free silicon precursor under conditionsallowing the chlorine-free silicon precursor to adsorb onto the surfaceof the substrate, thereby forming an adsorbed layer of the chlorine freesilicon precursor, and (ii) exposing the adsorbed layer of thechlorine-free silicon precursor to a nitrogen-containing reactant toform a silicon nitride film over the substrate using a plasma-freethermal reaction; and (c) treating the silicon nitride film by exposingthe silicon nitride film to a treatment gas and igniting a plasma at asecond temperature less than 100° C. to form a treated silicon nitridefilm.

In various embodiments, the first temperature is between 100° C. and250° C. In various embodiments, the second temperature is between 25° C.and 100° C. In some embodiments, the second temperature is between 50°C. and 100° C.

In various embodiments, the wet etch rate of the treated silicon nitridefilm in 100:1 hydrofluoric acid is less than about 30 Å/minute.

In some embodiments, treating the silicon nitride film reduces the wetetch rate of the silicon nitride film in 100:1 hydrofluoric acid by atleast 90%.

In various embodiments, the treatment gas is nitrogen and/or helium.

The method can also include repeating (i) and (ii) in deposition cyclesto deposit the conformal silicon nitride film. In various embodiments,(b) is performed after every deposition cycle. In some embodiments, (b)is performed every n deposition cycles of repeating (i) and (ii) in (a),and n is an integer greater than 2.

In various embodiments, the treated silicon nitride film has less than5% hydrogen in atomic content. In some embodiments, the conformalsilicon nitride film is deposited to a thickness less than about 50 Å.

The silicon nitride film may be deposited over a memory stack includinggermanium, antimony, and tellurium. In some embodiments, the siliconnitride film is deposited over one or more exposed layers ofchalcogenide material.

In various embodiments, the treated silicon nitride film has a densityof at least about 2.4 g/cc. In some embodiments, treating the siliconnitride film reduces the N—H content of the silicon nitride film asmeasured by FTIR.

In some embodiments, the silicon nitride film is exposed to the plasmafor a duration between about 1 second and about 10 seconds. In variousembodiments, the chlorine-free silicon precursor may be any one or moreof iodine-containing silicon precursors, bromine containing siliconprecursors, and iodine-and-bromine-containing silicon precursors.

In some embodiments, the chlorine-free silicon precursor is one or moreof compounds having a chemical formula of Si_(x)Br_(y)I_(z), where x=1,y is an integer between and including 1 and 4, and y+z=4; and compoundshaving a chemical formula of Si_(x)Br_(y)I_(z), where x=2, y is aninteger between and including 1 and 6, and y+z=6.

The chlorine-free silicon precursor may be any of tetrabromosilane(SiBr₄), SiBr₃I, SiBr₂I₂, SiBrI₃, hexabromodisilane (Si₂Br₆), Si₂Br₅I,Si₂Br₄I₂, Si₂Br₃I₃, Si₂Br₂I₄, Si₂BrI₅, and combinations thereof.

Another aspect involves a method of processing a substrate, the methodincluding: (a) providing the substrate to a chamber; (b) depositing aconformal silicon nitride film over the substrate at a first temperatureby: (i) exposing the substrate to alternating pulses of a chlorine-freesilicon precursor and a nitrogen-containing reactant to form a siliconnitride film over the substrate using a plasma-free thermal reaction;and (c) treating the silicon nitride film by exposing the siliconnitride film to a treatment gas and igniting a plasma at a secondtemperature less than 100° C. to form a treated silicon nitride film.

Another aspect involves an apparatus for patterning substrates, theapparatus including: one or more process chambers; one or more gasinlets into the one or more process chambers and associated flow controlhardware; a low frequency radio frequency (LFRF) generator; a highfrequency radio frequency (HFRF) generator; and a controller having atleast one processor and a memory, whereby the at least one processor andthe memory are communicatively connected with one another, the at leastone processor is at least operatively connected with the flow-controlhardware, the LFRF generator, and the HFRF generator, and the memorystores computer-executable instructions for controlling the at least oneprocessor to at least control the flow-control hardware, the HFRFgenerator, and the LFRF generator to: depositing a conformal siliconnitride film over the substrate at a first temperature by: introducing achlorine-free silicon precursor under conditions allowing thechlorine-free silicon precursor to adsorb onto a surface of a substrate,thereby forming an adsorbed layer of the chlorine free siliconprecursor, and introducing a nitrogen-containing reactant to form asilicon nitride film over the substrate using a plasma-free thermalreaction; and (c) treating the silicon nitride film by exposing thesilicon nitride film to a treatment gas and igniting a plasma at asecond temperature less than 100° C. to form a treated silicon nitridefilm.

These and other aspects are described further below with reference tothe drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an example substrate.

FIG. 2 is a process flow diagram depicting operations for a method inaccordance with disclosed embodiments.

FIG. 3 is a timing sequence diagram showing an example of cycles in amethod in accordance with certain disclosed embodiments.

FIG. 4 is a schematic diagram of an example process chamber forperforming disclosed embodiments.

FIG. 5 is a schematic diagram of an example process tool for performingdisclosed embodiments.

FIG. 6 is a plot depicting a Fourier transform infrared spectroscopyspectrum of experimental results for a silicon nitride film depositedusing certain disclosed embodiments.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth toprovide a thorough understanding of the presented embodiments. Thedisclosed embodiments may be practiced without some or all of thesespecific details. In other instances, well-known process operations havenot been described in detail to not unnecessarily obscure the disclosedembodiments. While the disclosed embodiments will be described inconjunction with the specific embodiments, it will be understood that itis not intended to limit the disclosed embodiments.

Semiconductor fabrication processes often involve deposition of siliconnitride material. In one example, silicon nitride may be used insemiconductor device fabrication as diffusion barriers, gate insulators,sidewall spacers, and encapsulation layers. Conformal silicon nitridelayers may also be used in other applications. For example, siliconnitride may be used during fabrication of memory structures. Siliconnitride is used as an encapsulation layer over memory devices.Conventional memory structures include metal oxide materials used forbit storage. However, as advanced memory structures are developed toaccommodate smaller device sizes and improve efficiency, new challengesarise. Advanced memory architectures such as magnetoresistiverandom-access memory and phase change random-access memory (PCRAM) relyon new materials (other than metal oxides) for bit storage. In the caseof PCRAM for example, the phase of a metal chalcogenide determines thebit state. Some example chalcogenides include sulfur (S), selenium (Se),and tellurium (Te). These new materials are air and moisture sensitiveand may require encapsulation layers. When combined with appropriatemetalloid ions such as germanium (Ge), antimony (Sb), etc., thesechalcogenides form a phase change layer. One example of a phase changelayer includes germanium, antimony, and tellurium (which may be referredto as a “GST layer” as used herein). If damaged, the phase change layermay not change phases. The phase change layer may also be sensitive tolight. To prevent damage to the phase change layer, a conformal siliconnitride memory encapsulation layer is deposited over the phase changelayer. It is desirable for a silicon nitride encapsulation layer to havevarious characteristics: conformal deposition, low wet etch rate, andlow or no hydrogen content. Deposition and treatment operations over thememory device are performed at low temperatures to reduce damage to theunderlying material.

However, many conventional deposition methods for depositing suchsilicon nitride layers as encapsulations layers for magnetic deviceseither deposit non-conformal films, such as in plasma enhanced chemicalvapor deposition (PECVD), or use chemistries that etch the chalcogenidematerial, such as chlorine-containing or hydrogen-containing plasmas.For example, the metal may undergo erosion as follows:

M_((solid)) +xCl_((gas))→MCl_(x(gas))  Eqn. 1

In another example, the metal may undergo oxidation or nitridation. Anexample of an oxidation reaction may be as follows:

M_((solid)) +xO_((gas))→MO_(x(solid))  Eqn. 2

Use of a chlorine-containing silicon precursor also often involvesdeposition at extremely high temperatures, such as at temperatureshigher than about 500° C. Deposition processes at such high temperaturesare usually not feasible for memory devices, as the underlayers may bedamaged from the heat. For example, the highest temperature fordepositing films over a GST layer may be about 250° C. to avoid damageto the GST layer due to heat. As a result, deposition usingchlorine-containing precursors has conventionally involved igniting aplasma to catalyze the reaction to form silicon nitride. For example,some conventional deposition involves alternating doses ofdichlorosilane (or another chlorine-containing precursor) and ammonia(NH₃) plasma, but both of these operations tend to generate speciescapable of etching chalcogenide material. Igniting plasma afteradsorbing a layer of dichlorosilane (SiCl₂H₂) to form silicon nitride byplasma enhanced atomic layer deposition results in formation of hydrogenradicals and NH₂ radicals as well as hydrogen chloride, which may thenattack metal chalcogenides and metal components of the chamber. Anexample is provided in FIG. 1.

FIG. 1 depicts a substrate 100 including an oxide layer 101. Thesubstrate 100 also includes a tungsten layer 103, carbon layer 105,chalcogenide layer 107, second carbon layer 115, second chalcogenidelayer 117, third carbon layer 125, and nitride layer 109.

As shown in FIG. 1, if a chlorine-containing silicon precursor is usedto deposit an encapsulation layer over the substrate, chlorine and/orhydrogen radicals generated when the plasma is ignited with the secondreactant may react to form hydrogen chloride such that chlorine mayreact with aluminum, germanium, or antimony, or other chamber materialmetals including iron or copper. These materials (e.g., AlCl₃, GeCl₄, orSbCl₃) may generate an evaporative layer, which form volatile metalsalts. These materials have a low boiling point; for example, theboiling point of AlCl₃ is 120° C., the boiling point of GeCl₄ is 87° C.,and the boiling point of SbCl₃ is 200° C. These volatile metal salts maythereby redeposit onto other layers of the substrate resulting indefects and performance issues. Thus, chlorine precursors suffer fromthe general issues of metal contamination in the films due to chamberetching which produces volatile metal chlorides (Al, Fe, and Cu).

Similarly, a plasma generated from a nitrogen-containing reactant suchas ammonia may form free hydrogen ions, radicals, and other plasmaspecies that may also etch the chalcogenide. For example, a hydrogenplasma may react with tellurium or selenium to form H₂Te and H₂Serespectively, thereby removing material from the stack and resulting inperformance issues and defects. These materials have a low boilingpoint; for example, H₂Te has a boiling point of −2° C., and H₂Se has aboiling point of −41° C. Generation of such material from exposure tohydrogen plasma may thereby etch the stack. Accordingly, conventionalchlorine- and hydrogen-free processes (e.g. using an N₂ plasma) do notgenerate a conformal film and are not effective as barriers.

A chlorine-free silicon precursor may be used for depositing a conformalsilicon nitride film using a thermal atomic layer deposition (ALD)process over memory devices. Discussion on using such precursors insilicon nitride deposition by ALD are further described in U.S. patentapplication Ser. No. 14/935,317, filed on Nov. 6, 2015 and titled“METHOD FOR ENCAPSULATING A CHALCOGENIDE MATERIAL” and U.S. patentapplication Ser. No. 15/272,222, filed on Sep. 21, 2016 and titled“BROMINE CONTAINING SILICON PRECURSORS FOR ENCAPSULATION LAYERS”, whichare herein incorporated by reference in their entireties.

While these precursors are used to deposit silicon nitride withoutdamaging the underlying substrate, the resulting silicon nitride filmstill has a high wet etch rate, which affects subsequent processing. Itis desirable to have a low wet etch rate silicon nitride material tosufficiently encapsulate the underlying device when the substrate isexposed to various chemicals in subsequent processing. For example, thefilm may be exposed to chemistries for performing chemical mechanicalplanarization. However, techniques for lowering the wet etch rate of thesilicon nitride film are lacking. For example, one technique is toplasma-treat the silicon nitride using nitrogen to reduce the wet etchrate after depositing the silicon nitride such that plasma treatment anddeposition are performed at the same temperature of about 250° C.Temperature is maximized to the highest temperature the substrate canallow (e.g., 250° C.) to reduce the hydrogen content in the film.However, such treatment damages the underlying material, such as a GSTlayer that may be on a PCRAM device because the nitrogen plasma reactswith germanium to form germanium nitride (GeN) on the surface. Germaniumnitride formation results in a crust over the material, therebyaffecting device performance.

Provided herein are methods and apparatuses for forming conformalsilicon nitride over a memory device such that the formed siliconnitride film has reduced wet etch rate without damaging the underlyingsubstrate. Methods are particularly applicable to encapsulation of PCRAMdevices, especially devices where the phase change layer is a GST layer.Methods involve forming a silicon nitride layer using a chlorine-freesilicon precursor and treating the silicon nitride layer using ahydrogen-free plasma at low temperatures, such as less than about 100°C. The improvement in wet etch rate reduction is surprising andcounter-intuitive, as it is usually expected for wet etch rate toincrease at lower temperatures (hence conventional techniques ofperforming deposition and any treatment at the maximum temperatureallowable by the underlying substrate without damaging it). Instead,disclosed embodiments involve using low temperatures to improve wet etchrate performance.

FIG. 2 provides a process flow diagram of operations that are performedin accordance with certain disclosed embodiments. In operation 201, asubstrate is provided to a process chamber. The substrate may be asilicon wafer, e.g., a 200-mm wafer, a 300-mm wafer, or a 450-mm wafer,including wafers having one or more layers of material, such asdielectric, conducting, or semi-conducting material deposited thereon.Non-limiting examples of underlayers include dielectric layers andconducting layers, e.g., silicon oxides, silicon nitrides, siliconcarbides, metal oxides, metal nitrides, metal carbides, and metallayers. In some embodiments, the substrate includes a stack such as theone depicted in FIG. 1. In some embodiments, the substrate includes twoor more stacks, each of the stacks including layers such as the layersdepicted in FIG. 1. The space between stacks may be narrow such thataspect ratios between stacks may be between about 3:1 and about 10:1,such as about 5:1.

During operations 203-213 of FIG. 2A, an inert gas may be flowed. Invarious embodiments, the inert gas is used as a carrier gas. Examplecarrier gases include argon, helium, and neon. In some embodiments, ahydrogen-containing carrier gas may be used. In some embodiments, thecarrier gas is used as a purge gas in some operations. In someembodiments, the carrier gas is diverted. The inert gas may be providedto assist with pressure and/or temperature control of the processchamber, evaporation of a liquid reactant, more rapid delivery of thereactant and/or as a sweep gas for removing process gases from theprocess chamber and/or process chamber plumbing. Various disclosedembodiments may be performed at a pressure between about 0.1 Torr andabout 20 Torr. Operations 203-213 may be performed at a substratetemperature less than about 300° C., such as between about 50° C. andabout 300° C., for example, about 250° C. In such embodiments, thepedestal may be set to a temperature of less than about 300° C. tocontrol the substrate temperature. For example, for MRAM and PCRAMapplications, the materials on the substrate may be sensitive to hightemperatures. In some embodiments, silicon nitride is deposited at atemperature between about 200° C. and about 275° C.

In operation 203, the substrate is exposed to an iodine-containingand/or bromine-containing silicon precursor such that theiodine-containing and/or bromine-containing silicon precursor adsorbsonto the substrate surface. Iodine-containing and/or bromine-containingsilicon precursors may be completely substituted with bromine and/oriodine atoms in various embodiments. That is, iodine-containingprecursors and/or bromine-containing precursors may have no hydrogenatoms. Disclosed embodiments involve precursors not conventionally usedfor deposition of silicon nitride by ALD. Using an iodine-containingand/or bromine-containing silicon precursor allows for chlorine-freedeposition. Example iodine-containing silicon precursors includediiodosilane (DIS), tetraiodosilane, hexaiododisilane, and others. Invarious embodiments, bromine-containing silicon precursors are fullyhalogenated. Bromine-containing silicon precursors may have the chemicalformula Si_(x)Br_(y)I_(z), where if x=1, y is an integer between andincluding 1 and 4, and y+z=4, or where if x=2, y is an integer betweenand including 1 and 6, and y+z=6. Example bromine-containing siliconprecursors include tetrabromosilane (SiBr₄), SiBr₃I, SiBr₂I₂, SiBrI₃,hexabromodisilane (Si₂Br₆), Si₂Br₅I, Si₂Br₄I₂, Si₂Br₃I₃, Si₂Br₂I₄,Si₂BrI₅, and combinations thereof.

Operation 203 may be part of an ALD cycle. As discussed above, generallyan ALD cycle is the minimum set of operations used to perform a surfacedeposition reaction one time. In some embodiments, the result of onecycle is production of at least a partial silicon nitride film layer ona substrate surface. The cycle may include certain ancillary operationssuch as sweeping one of the reactants or byproducts and/or treating thepartial film as deposited. Generally, a cycle contains one instance of aunique sequence of operations. As discussed above, generally a cycle isthe minimum set of operations used to perform a surface depositionreaction one time. The result of one cycle is production of at least apartial film layer, e.g., a partial silicon nitride film layer, on asubstrate surface.

During operation 203, the substrate is exposed to a silicon-containingprecursor such that the silicon-containing precursor is adsorbed ontothe substrate surface to form an adsorbed layer. In some embodiments, aniodine-containing and/or bromine-containing silicon precursor adsorbsonto the substrate surface in a self-limiting manner such that onceactive sites are occupied by the iodine-containing and/orbromine-containing silicon precursor, little or no additionaliodine-containing and/or bromine-containing silicon precursor will beadsorbed on the substrate surface. For example, iodine-containing and/orbromine-containing silicon precursor may be adsorbed onto about 60% ofthe substrate surface. In various embodiments, when theiodine-containing and/or bromine-containing silicon precursor is flowedto the chamber, the iodine-containing and/or bromine-containing siliconprecursor adsorbs onto active sites on the surface of the substrate,forming a thin layer of the iodine-containing and/or bromine-containingsilicon precursor on the surface. In various embodiments, this layer maybe less than a monolayer, and may have a thickness between about 0.2 Åand about 0.4 Å. Methods provided herein may be performed at atemperature less than about 300° C., such as at about 250° C. In someembodiments, disclosed embodiments are performed at a temperaturebetween about 50° C. and about 300° C., such as at a temperature betweenabout 200° C. and about 275° C. In some embodiments, silicon nitride isdeposited at a temperature between about 50° C. and about 300° C. Insome embodiments, silicon nitride is deposited at a temperature betweenabout 200° C. and about 275° C.

In operation 205, the process chamber is optionally purged to removeexcess iodine-containing silicon precursor in gas phase that did notadsorb onto the surface of the substrate. Purging the chamber mayinvolve flowing a purge gas or a sweep gas, which may be a carrier gasused in other operations or may be a different gas. In some embodiments,purging may involve evacuating the chamber. Example purge gases includeargon, nitrogen, hydrogen, and helium. In some embodiments, operation205 may include one or more evacuation subphases for evacuating theprocess chamber. Alternatively, it will be appreciated that operation205 may be omitted in some embodiments. Operation 205 may have anysuitable duration, such as between about 0 seconds and about 60 seconds,for example about 0.01 seconds. In some embodiments, increasing a flowrate of one or more purge gases may decrease the duration of operation205. For example, a purge gas flow rate may be adjusted according tovarious reactant thermodynamic characteristics and/or geometriccharacteristics of the process chamber and/or process chamber plumbingfor modifying the duration of operation 205. In one non-limitingexample, the duration of a purge phase may be adjusted by modulatingpurge gas flow rate. This may reduce deposition cycle time, which mayimprove substrate throughput. After a purge, the iodine-containingand/or bromine-containing silicon precursors remain adsorbed onto thesubstrate surface.

In operation 211, the substrate is exposed to a second reactant to reactwith the adsorbed layer of the iodine-containing and/orbromine-containing silicon precursor. Note that the term “secondreactant” may be used to describe one or more gases introduced to thechamber when plasma is ignited in an ALD cycle. In various embodiments,the second reactant is a nitrogen-containing reactant. In someembodiments, operation 203 may be performed before performing operation211. In some embodiments, operation 211 may be performed beforeperforming operation 203. In some embodiments, operation 211 may beperformed before depositing any silicon nitride.

In some embodiments, the reaction may be thermal. Methods involvingthermal ALD using either ammonia (NH₃) or hydrazines (e.g., H₄N₂) reducecontamination and reduce the presence of hydrogen radicals duringdeposition, thereby reducing etching of the chalcogenide and/or metalson the substrate and/or in the chamber. For a thermal process,deposition may be performed at a temperature of at least about 250° C.,such as about 300° C. In some embodiments, disclosed embodiments areperformed at a temperature between about 50° C. and about 300° C., suchas at a temperature between about 200° C. and about 275° C. In someembodiments, silicon nitride is deposited at a temperature between about50° C. and about 300° C. In some embodiments, silicon nitride isdeposited at a temperature between about 200° C. and about 275° C.

In some embodiments, a plasma may be optionally ignited in operation211. Plasma energy may be provided to activate the second reactant, suchas a nitrogen-containing gas, into ions and radicals and other activatedspecies, which react with the adsorbed layer of the first precursor. Indisclosed embodiments involving a plasma, the plasma may include lessthan about 1% hydrogen radicals, thereby reducing etching ofchalcogenide or metal material during deposition. In variousembodiments, the plasma is an in-situ plasma, such that the plasma isformed directly above the substrate surface in the chamber. The in-situplasma may be ignited at a power per substrate area between about 0.2122W/cm² and about 2.122 W/cm². For example, the power may range from about150 W to about 6000 W, or from about 600 W to about 6000 W, or fromabout 800 W to about 4000 W, for a chamber processing four 300 mmwafers. For example, plasmas for ALD processes may be generated byapplying a radio frequency (RF) field to a gas using two capacitivelycoupled plates. Ionization of the gas between plates by the RF fieldignites the plasma, creating free electrons in the plasma dischargeregion. These electrons are accelerated by the RF field and may collidewith gas phase reactant molecules. Collision of these electrons withreactant molecules may form radical species that participate in thedeposition process. It will be appreciated that the RF field may becoupled via any suitable electrodes. In various embodiments, a highfrequency plasma is used having a frequency of at least about 13.56 MHz,or at least about 27 MHz, or at least about 40 MHz, or at least about 60MHz. In some embodiments, a microwave-based plasma may be used.Non-limiting examples of electrodes include process gas distributionshowerheads and substrate support pedestals. It will be appreciated thatplasmas for ALD processes may be formed by one or more suitable methodsother than capacitive coupling of an RF field to a gas. In someembodiments, the plasma is a remote plasma, such that a second reactantis ignited in a remote plasma generator upstream of the chamber, thendelivered to the chamber where the substrate is housed.

Where a plasma is used, a dose of an iodine-containing silicon precursormay be followed by a dose of nitrogen (N₂) or hydrogen (H₂) plasma. Thecorresponding iodine-containing and/or bromine-containing metal saltsthat may generate from reacting with chalcogenides on the substrate ormetals of the chamber components may not be sufficiently volatile toresult in wafer contamination. For example, iodine-containing saltsincluding aluminum, germanium, or antimony have higher boiling pointsthan corresponding chlorine-containing salts. As a result,iodine-containing salts may form a passivation layer, but not anevaporative layer, and the salts are less likely to redeposit ontomaterials on the substrate. In some cases, aluminum may react withchlorine such that the chamber is etched and therefore damaged, andaluminum may also decompose onto the wafer.

Returning to FIG. 2A, in operation 213, the chamber is optionally purgedto remove the etched species and any residual byproducts. Operation 213may be purged using any of the conditions described above with respectto operation 205.

After performing operation 213, it is determined whether the desiredthickness of film has been deposited. If not, operations 203-213 arerepeated in sufficient cycles to deposit a desired thickness of film.Any suitable number of deposition cycles may be included in an ALDprocess to deposit a desired film thickness of silicon nitride. Forexample, about fifty deposition cycles may be performed to deposit afilm on the substrate using disclosed embodiments. In some embodimentsthe thickness of the deposited silicon nitride film may be greater thanabout 30 Å on a sidewall over a stack of films for fabrication of amemory device.

In operation 299, the substrate is exposed to a plasma treatment at asubstrate temperature less than about 100° C. A treatment gas is flowedand a plasma is ignited. The treatment gas may be nitrogen and/orhelium. In various embodiments, operation 299 involves changing thesubstrate temperature by adjusting the temperature to which the pedestalholding the substrate is set. In some embodiments, the plasma treatmentis performed at a substrate temperature between about 25° C. and about100° C., or between about 50° C. and about 100° C. The substrate isexposed to the treatment plasma after every n cycles of performingoperations 203-213, where n is any integer of 1 or greater. In someembodiments, the treatment is performed after all cycles of operations203-213 over a formed silicon nitride film.

Treating the deposited silicon nitride film with a nitrogen and/orhelium plasma at a higher temperature such as about 250° C. results innitridation of the underlayers, such as a GST layer, and formation of agermanium nitride crust, which affects device performance. Althoughdeposition and treatment temperatures are generally selected to be ashigh as possible to minimize the hydrogen content of the silicon nitridefilm and reduce the wet etch rate, treatment performed at lowtemperatures of less than about 100° C. as described herein with respectto certain disclosed embodiments yields surprisingly low wet etch ratesilicon nitride films. Treatments at lower temperatures as describedherein are not expected to substantially affect the wet etch rate.However, wet etch rate of the treated silicon nitride film issurprisingly substantially reduced when treatment is performed attemperatures less than about 100° C. Treating silicon nitride filmsreduces the wet etch rate by at least 90%. Disclosed embodiments resultin treated silicon nitride films having a wet etch rate in 100:1 dilutehydrofluoric acid of less than about 30 Å/minute. Additionally, plasmatreatment eliminates formation of the germanium nitride crust, andreduces the hydrogen content of the film, which may be incorporated fromsilicon precursors or reactants used for depositing the silicon nitridefilm. Untreated films may have a hydrogen content of about 20% or morein atomic content. In contrast, films treated using certain disclosedembodiments as described herein have a hydrogen content of less thanabout 5% in atomic content. Untreated films may also have a lowerdensity, such as between about 2.0 g/cc and about 2.2 g/cc. In variousembodiments, film treated in accordance with certain disclosedembodiments may have a density of at least about 2.4 g/cc.

Operation 299 involves setting the temperature of the pedestal holdingthe substrate to a temperature less than about 100° C., introducing anitrogen or helium gas to the chamber, and igniting a plasma. In variousembodiments, the plasma does not contain hydrogen, as ahydrogen-containing plasma will etch underlying material, such as a GSTlayer. The plasma in some embodiments is an in-situ plasma, such thatthe plasma is formed directly above the substrate surface in thechamber. The in-situ plasma may be ignited at a power per substrate areabetween about 0.10 W/cm² and about 2.0 W/cm². For example, the power mayrange from about 75 W to about 1500 W; or from about 300 W to about 6000W for a chamber processing four 300 mm wafers. For example, plasmas forALD processes may be generated by applying a radio frequency (RF) fieldto a gas using two capacitively coupled plates. Ionization of the gasbetween plates by the RF field ignites the plasma, creating freeelectrons in the plasma discharge region. These electrons areaccelerated by the RF field and may collide with gas phase molecules.Collision of these electrons with molecules may form radical speciesthat participate in the treatment process. It will be appreciated thatthe RF field may be coupled via any suitable electrodes. In variousembodiments, a high frequency plasma is used having a frequency of atleast about 13.56 MHz, or at least about 27 MHz, or at least about 40MHz, or at least about 60 MHz. In some embodiments, a microwave-basedplasma may be used. Non-limiting examples of electrodes include processgas distribution showerheads and substrate support pedestals. It will beappreciated that plasmas for ALD processes may be formed by one or moresuitable methods other than capacitive coupling of an RF field to a gas.In some embodiments, the plasma is a remote plasma, such that nitrogenor helium is ignited in a remote plasma generator upstream of thechamber, then delivered to the chamber where the substrate is housed.

The silicon nitride film is treated for a duration between about 1second and about 10 seconds. In some embodiments, the silicon nitridefilm is deposited to a thickness of about 100 Å after performingoperations 203-299 in cycles.

FIG. 3 provides a timing scheme diagram for performing a low temperaturetreatment phase after two cycles of deposition. Note that while twocycles are depicted, any number of cycles may be performed to depositsilicon nitride. Additionally, while one treatment phase is depicted fortwo cycles of deposition, it will be understood that the treatment maybe performed after every cycle, or after every 2 cycles, or after every3 cycles, or after every n cycles, for any integer n greater than orequal to 1.

FIG. 3 depicts a process 300 including two deposition cycles—depositioncycle 310A and deposition 310B with a low temperature treatment phase390 following the two deposition cycles. FIG. 3 also shows carrier gasflow, iodosilane/bromosilane precursor gas flow, nitrogen gas flow,temperature, and plasma. It will be understood that the precursor mayinclude an iodosilane, bromosilane, or combination thereof. The exampleshown in FIG. 3 involves using a nitrogen plasma for the low temperaturetreatment phase 390, but it will be understood that in some embodiments,another non-hydrogen-containing gas such as helium may be used to ignitethe plasma.

Deposition cycle 310A includes an iodosilane/bromosilane precursorexposure phase 357A, purge phase 359A, nitrogen reactant exposure phase361A, and purge phase 363A. These operations may constitute one ALDcycle. During iodosilane/bromosilane precursor exposure phase 357A, acarrier gas may be flowed. In some embodiments, a carrier gas may beflowed with the precursor and then diverted. Iodosilane/bromosilaneprecursor exposure phase 357A may correspond to operation 203 of FIG. 2.During iodosilane/bromosilane precursor exposure phase 357A, theiodosilane/bromosilane precursor gas flow is turned on, nitrogen flow isturned off, and temperature is set on “high”, which may be about 250°C., or the highest possible temperature for forming the silicon nitridefilm without damaging the substrate. In purge phase 359A, theiodosilane/bromosilane precursor flow is turned off, nitrogen flowremains off, temperature remains at 250° C., and the carrier gas may beflowed to the chamber to remove precursors that did not adsorb to thesubstrate. This phase may correspond to operation 205 of FIG. 2. Innitrogen reactant exposure phase 361A, the carrier gas may continue toflow and/or may be used to introduce nitrogen to the chamber.Iodosilane/bromosilane precursor flow remains off, nitrogen gas flow isturned on and temperature remains at 250° C. It will be noted thatplasma remains off during the deposition cycle to allow a thermaldeposition process. Nitrogen reactant exposure phase 361A may correspondto operation 211 of FIG. 2. In purge phase 363A, a carrier gas is flowedto remove byproducts from reacting the iodosilane/bromosilane precursorwith the nitrogen reactant, iodosilane/bromosilane precursor flowremains off, nitrogen gas flow is turned off, and temperature remains at250° C. This phase may correspond to operation 213 of FIG. 2.

Following deposition cycle 310A, the ALD cycle is repeated fordeposition cycle 310B, which may correspond to optionally repeatingoperations 203-213 of FIG. 2. As shown in FIG. 3, deposition cycle 310Bincludes phases mirroring those of deposition cycle 310A, as the ALDcycle is repeated to include iodosilane/bromosilane precursor exposurephase 357B, purge phase 359B, nitrogen reactant exposure phase 361B, andpurge phase 363B. Following deposition cycle 310B, a low temperaturetreatment phase 390 is performed such that carrier gas may be flowedand/or be used to introduce nitrogen and be diverted,iodosilane/bromosilane precursor flow remains off, nitrogen flow isturned on, and temperature is reduced to a temperature less than about100° C. Here, low temperature treatment phase 390 may correspond tooperation 299 of FIG. 2. Note that although not shown in FIG. 3,deposition cycle 310A, deposition cycle 310B, and low temperaturepost-treatment phase 390 may be repeated in subsequent cycles until thedesired thickness of a silicon nitride film having low hydrogen contentand low wet etch rate is achieved.

Apparatus

FIG. 4 depicts a schematic illustration of an embodiment of an atomiclayer deposition (ALD) process station 400 having a process chamber body402 for maintaining a low-pressure environment. A plurality of ALDprocess stations 400 may be included in a common low pressure processtool environment. For example, FIG. 5 depicts an embodiment of amulti-station processing tool 500. In some embodiments, one or morehardware parameters of ALD process station 400 including those discussedin detail below may be adjusted programmatically by one or more computercontrollers 450.

ALD process station 400 fluidly communicates with reactant deliverysystem 401 a for delivering process gases to a distribution showerhead406. Reactant delivery system 401 a includes a mixing vessel 404 forblending and/or conditioning process gases, such as an iodine-containingand/or bromine-containing silicon precursor gas, or second reactant gas(e.g., ammonia or hydrazine), for delivery to showerhead 406. One ormore mixing vessel inlet valves 420 may control introduction of processgases to mixing vessel 404. Nitrogen plasma or hydrogen plasma may alsobe delivered to the showerhead 406 or may be generated in the ALDprocess station 400.

As an example, the embodiment of FIG. 4 includes a vaporization point403 for vaporizing liquid reactant to be supplied to the mixing vessel404. In some embodiments, vaporization point 403 may be a heatedvaporizer. The saturated reactant vapor produced from such vaporizersmay condense in downstream delivery piping. Exposure of incompatiblegases to the condensed reactant may create small particles. These smallparticles may clog piping, impede valve operation, contaminatesubstrates, etc. Some approaches to addressing these issues involvepurging and/or evacuating the delivery piping to remove residualreactant. However, purging the delivery piping may increase processstation cycle time, degrading process station throughput. Thus, in someembodiments, delivery piping downstream of vaporization point 403 may beheat traced. In some examples, mixing vessel 404 may also be heattraced. In one non-limiting example, piping downstream of vaporizationpoint 403 has an increasing temperature profile extending fromapproximately 100° C. to approximately 150° C. at mixing vessel 404.

In some embodiments, liquid precursor or liquid reactant may bevaporized at a liquid injector. For example, a liquid injector mayinject pulses of a liquid reactant into a carrier gas stream upstream ofthe mixing vessel. In one embodiment, a liquid injector may vaporize thereactant by flashing the liquid from a higher pressure to a lowerpressure. In another example, a liquid injector may atomize the liquidinto dispersed microdroplets that are subsequently vaporized in a heateddelivery pipe. Smaller droplets may vaporize faster than largerdroplets, reducing a delay between liquid injection and completevaporization. Faster vaporization may reduce a length of pipingdownstream from vaporization point 403. In one scenario, a liquidinjector may be mounted directly to mixing vessel 404. In anotherscenario, a liquid injector may be mounted directly to showerhead 406.

In some embodiments, a liquid flow controller (LFC) upstream ofvaporization point 403 may be provided for controlling a mass flow ofliquid for vaporization and delivery to process station 400. Forexample, the LFC may include a thermal mass flow meter (MFM) locateddownstream of the LFC. A plunger valve of the LFC may then be adjustedresponsive to feedback control signals provided by aproportional-integral-derivative (PID) controller in electricalcommunication with the MFM. However, it may take one second or more tostabilize liquid flow using feedback control. This may extend a time fordosing a liquid reactant. Thus, in some embodiments, the LFC may bedynamically switched between a feedback control mode and a directcontrol mode. In some embodiments, this may be performed by disabling asense tube of the LFC and the PID controller.

Showerhead 406 distributes process gases toward substrate 412. In theembodiment shown in FIG. 4, the substrate 412 is located beneathshowerhead 406 and is shown resting on a pedestal 408. Showerhead 406may have any suitable shape, and may have any suitable number andarrangement of ports for distributing process gases to substrate 412.

In some embodiments, pedestal 408 may be raised or lowered to exposesubstrate 412 to a volume between the substrate 412 and the showerhead406. It will be appreciated that, in some embodiments, pedestal heightmay be adjusted programmatically by a suitable computer controller 450.

In another scenario, adjusting a height of pedestal 408 may allow aplasma density to be varied during plasma activation cycles in theprocess in embodiments where a plasma is ignited. At the conclusion ofthe process phase, pedestal 408 may be lowered during another substratetransfer phase to allow removal of substrate 412 from pedestal 408.

In some embodiments, pedestal 408 may be temperature controlled viaheater 410. In some embodiments, the pedestal 408 may be heated to atemperature of at least about 250° C., or in some embodiments, less thanabout 300° C., such as about 250° C., during deposition of siliconnitride films as described in disclosed embodiments. In someembodiments, the pedestal is set at a temperature between about 50° C.and about 300° C., such as at a temperature between about 200° C. andabout 275° C. In some embodiments, the pedestal is set at a temperaturebetween about 50° C. and about 300° C. In some embodiments, the pedestalis set at a temperature between about 200° C. and about 275° C.

Further, in some embodiments, pressure control for process station 400may be provided by butterfly valve 418. As shown in the embodiment ofFIG. 4, butterfly valve 418 throttles a vacuum provided by a downstreamvacuum pump (not shown). However, in some embodiments, pressure controlof process station 400 may also be adjusted by varying a flow rate ofone or more gases introduced to the process station 400.

In some embodiments, a position of showerhead 406 may be adjustedrelative to pedestal 408 to vary a volume between the substrate 412 andthe showerhead 406. Further, it will be appreciated that a verticalposition of pedestal 408 and/or showerhead 406 may be varied by anysuitable mechanism within the scope of the present disclosure. In someembodiments, pedestal 408 may include a rotational axis for rotating anorientation of substrate 412. It will be appreciated that, in someembodiments, one or more of these example adjustments may be performedprogrammatically by one or more suitable computer controllers 450.

In some embodiments where plasma may be used as discussed above,showerhead 406 and pedestal 408 electrically communicate with a radiofrequency (RF) power supply 414 and matching network 416 for powering aplasma. In some embodiments, the plasma energy may be controlled bycontrolling one or more of a process station pressure, a gasconcentration, an RF source power, an RF source frequency, and a plasmapower pulse timing. For example, RF power supply 414 and matchingnetwork 416 may be operated at any suitable power to form a plasmahaving a desired composition of radical species. Examples of suitablepowers are included above. Likewise, RF power supply 414 may provide RFpower of any suitable frequency. In some embodiments, RF power supply414 may be configured to control high- and low-frequency RF powersources independently of one another. Example low-frequency RFfrequencies may include, but are not limited to, frequencies between 0kHz and 500 kHz. Example high-frequency RF frequencies may include, butare not limited to, frequencies between 1.8 MHz and 2.45 GHz, or greaterthan about 13.56 MHz, or greater than 27 MHz, or greater than 40 MHz, orgreater than 60 MHz. It will be appreciated that any suitable parametersmay be modulated discretely or continuously to provide plasma energy forthe surface reactions.

In some embodiments, the plasma may be monitored in-situ by one or moreplasma monitors. In one scenario, plasma power may be monitored by oneor more voltage, current sensors (e.g., VI probes). In another scenario,plasma density and/or process gas concentration may be measured by oneor more optical emission spectroscopy sensors (OES). In someembodiments, one or more plasma parameters may be programmaticallyadjusted based on measurements from such in-situ plasma monitors. Forexample, an OES sensor may be used in a feedback loop for providingprogrammatic control of plasma power. It will be appreciated that, insome embodiments, other monitors may be used to monitor the plasma andother process characteristics. Such monitors may include, but are notlimited to, infrared (IR) monitors, acoustic monitors, and pressuretransducers.

In some embodiments, instructions for a controller 450 may be providedvia input/output control (IOC) sequencing instructions. In one example,the instructions for setting conditions for a process phase may beincluded in a corresponding recipe phase of a process recipe. In somecases, process recipe phases may be sequentially arranged, so that allinstructions for a process phase are executed concurrently with thatprocess phase. In some embodiments, instructions for setting one or morereactor parameters may be included in a recipe phase. For example, afirst recipe phase may include instructions for setting a flow rate ofan inert and/or a reactant gas (e.g., the first precursor such as aniodine-containing and/or bromine-containing silicon precursor),instructions for setting a flow rate of a carrier gas (such as argon),and time delay instructions for the first recipe phase. A second,subsequent recipe phase may include instructions for modulating orstopping a flow rate of an inert and/or a reactant gas, and instructionsfor modulating a flow rate of a carrier or purge gas and time delayinstructions for the second recipe phase. A third recipe phase mayinclude instructions for modulating a flow rate of a second reactant gassuch as ammonia, instructions for modulating the flow rate of a carrieror purge gas, and time delay instructions for the third recipe phase. Afourth, subsequent recipe phase may include instructions for modulatingor stopping a flow rate of an inert and/or a reactant gas, andinstructions for modulating a flow rate of a carrier or purge gas andtime delay instructions for the fourth recipe phase. A fifth, subsequentrecipe phase may include instructions for modulating or stopping a flowrate of an inert and/or a reactant gas, instructions for modulating aflow rate of a carrier or purge gas and time delay instructions for thefourth recipe phase, instructions for setting a flow rate of a treatmentgas, reducing the pedestal temperature to a temperature less than about100° C. and igniting a plasma. It will be appreciated that these recipephases may be further subdivided and/or iterated in any suitable waywithin the scope of the disclosed embodiments. In some embodiments, thecontroller 450 may include any of the features described below withrespect to system controller 550 of FIG. 5.

As described above, one or more process stations may be included in amulti-station processing tool. FIG. 5 shows a schematic view of anembodiment of a multi-station processing tool 500 with an inbound loadlock 502 and an outbound load lock 504, either or both of which mayinclude a remote plasma source. A robot 506 at atmospheric pressure isconfigured to move wafers from a cassette loaded through a pod 508 intoinbound load lock 502 via an atmospheric port 510. A wafer is placed bythe robot 506 on a pedestal 512 in the inbound load lock 502, theatmospheric port 510 is closed, and the load lock is pumped down. Wherethe inbound load lock 502 includes a remote plasma source, the wafer maybe exposed to a remote plasma treatment in the load lock prior to beingintroduced into a processing chamber 514. Further, the wafer also may beheated in the inbound load lock 502 as well, for example, to removemoisture and adsorbed gases. Next, a chamber transport port 516 toprocessing chamber 514 is opened, and another robot (not shown) placesthe wafer into the reactor on a pedestal of a first station shown in thereactor for processing. While the embodiment depicted in FIG. 5 includesload locks, it will be appreciated that, in some embodiments, directentry of a wafer into a process station may be provided.

The depicted processing chamber 514 includes four process stations,numbered from 1 to 4 in the embodiment shown in FIG. 5. Each station hasa heated pedestal (shown at 518 for station 1), and gas line inlets. Itwill be appreciated that in some embodiments, each process station mayhave different or multiple purposes. For example, in some embodiments, aprocess station may be switchable between an ALD and plasma-enhanced ALDprocess mode. Additionally or alternatively, in some embodiments,processing chamber 514 may include one or more matched pairs of ALD andplasma-enhanced ALD process stations. While the depicted processingchamber 514 includes four stations, it will be understood that aprocessing chamber according to the present disclosure may have anysuitable number of stations. For example, in some embodiments, aprocessing chamber may have five or more stations, while in otherembodiments a processing chamber may have three or fewer stations.

FIG. 5 depicts an embodiment of a wafer handling system 590 fortransferring wafers within processing chamber 514. In some embodiments,wafer handling system 590 may transfer wafers between various processstations and/or between a process station and a load lock. It will beappreciated that any suitable wafer handling system may be employed.Non-limiting examples include wafer carousels and wafer handling robots.FIG. 5 also depicts an embodiment of a system controller 550 employed tocontrol process conditions and hardware states of process tool 500.System controller 550 may include one or more memory devices 556, one ormore mass storage devices 554, and one or more processors 552. Processor552 may include a CPU or computer, analog, and/or digital input/outputconnections, stepper motor controller boards, etc.

In some embodiments, system controller 550 controls all of theactivities of process tool 500. System controller 550 executes systemcontrol software 558 stored in mass storage device 554, loaded intomemory device 556, and executed on processor 552. Alternatively, thecontrol logic may be hard coded in the controller 550. ApplicationsSpecific Integrated Circuits, Programmable Logic Devices (e.g.,field-programmable gate arrays, or FPGAs) and the like may be used forthese purposes. In the following discussion, wherever “software” or“code” is used, functionally comparable hard coded logic may be used inits place. System control software 558 may include instructions forcontrolling the timing, mixture of gases, gas flow rates, chamber and/orstation pressure, chamber and/or station temperature, wafer temperature,target power levels, RF power levels, substrate pedestal, chuck and/orsusceptor position, and other parameters of a particular processperformed by process tool 500. System control software 558 may beconfigured in any suitable way. For example, various process toolcomponent subroutines or control objects may be written to controloperation of the process tool components used to carry out variousprocess tool processes. System control software 558 may be coded in anysuitable computer readable programming language.

In some embodiments, system control software 558 may includeinput/output control (IOC) sequencing instructions for controlling thevarious parameters described above. Other computer software and/orprograms stored on mass storage device 554 and/or memory device 556associated with system controller 550 may be employed in someembodiments. Examples of programs or sections of programs for thispurpose include a substrate positioning program, a process gas controlprogram, a pressure control program, a heater control program, and aplasma control program.

A substrate positioning program may include program code for processtool components that are used to load the substrate onto pedestal 518and to control the spacing between the substrate and other parts ofprocess tool 500.

A process gas control program may include code for controlling gascomposition (e.g., iodine-containing silicon precursor gases, andnitrogen-containing gases, carrier gases and purge gases as describedherein) and flow rates and optionally for flowing gas into one or moreprocess stations prior to deposition in order to stabilize the pressurein the process station. A pressure control program may include code forcontrolling the pressure in the process station by regulating, forexample, a throttle valve in the exhaust system of the process station,a gas flow into the process station, etc.

A heater control program may include code for controlling the current toa heating unit that is used to heat the substrate. Alternatively, theheater control program may control delivery of a heat transfer gas (suchas helium) to the substrate.

A plasma control program may include code for setting RF power levelsapplied to the process electrodes in one or more process stations inaccordance with the embodiments herein.

A pressure control program may include code for maintaining the pressurein the reaction chamber in accordance with the embodiments herein.

In some embodiments, there may be a user interface associated withsystem controller 550. The user interface may include a display screen,graphical software displays of the apparatus and/or process conditions,and user input devices such as pointing devices, keyboards, touchscreens, microphones, etc.

In some embodiments, parameters adjusted by system controller 550 mayrelate to process conditions. Non-limiting examples include process gascomposition and flow rates, temperature, pressure, plasma conditions(such as RF bias power levels), etc. These parameters may be provided tothe user in the form of a recipe, which may be entered utilizing theuser interface.

Signals for monitoring the process may be provided by analog and/ordigital input connections of system controller 550 from various processtool sensors. The signals for controlling the process may be output onthe analog and digital output connections of process tool 500.Non-limiting examples of process tool sensors that may be monitoredinclude mass flow controllers, pressure sensors (such as manometers),thermocouples, etc. Appropriately programmed feedback and controlalgorithms may be used with data from these sensors to maintain processconditions.

System controller 550 may provide program instructions for implementingthe above-described deposition processes. The program instructions maycontrol a variety of process parameters, such as DC power level, RF biaspower level, pressure, temperature, etc. The instructions may controlthe parameters to operate in-situ deposition of film stacks according tovarious embodiments described herein.

The system controller 550 will typically include one or more memorydevices and one or more processors configured to execute theinstructions so that the apparatus will perform a method in accordancewith disclosed embodiments. Machine-readable media containinginstructions for controlling process operations in accordance withdisclosed embodiments may be coupled to the system controller 550.

In some implementations, the system controller 550 is part of a system,which may be part of the above-described examples. Such systems caninclude semiconductor processing equipment, including a processing toolor tools, chamber or chambers, a platform or platforms for processing,and/or specific processing components (a wafer pedestal, a gas flowsystem, etc.). These systems may be integrated with electronics forcontrolling their operation before, during, and after processing of asemiconductor wafer or substrate. The electronics may be referred to asthe “controller,” which may control various components or subparts ofthe system or systems. The system controller 550, depending on theprocessing conditions and/or the type of system, may be programmed tocontrol any of the processes disclosed herein, including the delivery ofprocessing gases, temperature settings (e.g., heating and/or cooling),pressure settings, vacuum settings, power settings, radio frequency (RF)generator settings, RF matching circuit settings, frequency settings,flow rate settings, fluid delivery settings, positional and operationsettings, wafer transfers into and out of a tool and other transfertools and/or load locks connected to or interfaced with a specificsystem.

Broadly speaking, the system controller 550 may be defined aselectronics having various integrated circuits, logic, memory, and/orsoftware that receive instructions, issue instructions, controloperation, enable cleaning operations, enable endpoint measurements, andthe like. The integrated circuits may include chips in the form offirmware that store program instructions, digital signal processors(DSPs), chips defined as application specific integrated circuits(ASICs), and/or one or more microprocessors, or microcontrollers thatexecute program instructions (e.g., software). Program instructions maybe instructions communicated to the system controller 550 in the form ofvarious individual settings (or program files), defining operationalparameters for carrying out a particular process on or for asemiconductor wafer or to a system. The operational parameters may, insome embodiments, be part of a recipe defined by process engineers toaccomplish one or more processing steps during the fabrication of one ormore layers, materials, metals, oxides, silicon, silicon dioxide,surfaces, circuits, and/or dies of a wafer.

The system controller 550, in some implementations, may be a part of orcoupled to a computer that is integrated with, coupled to the system,otherwise networked to the system, or a combination thereof. Forexample, the system controller 550 may be in the “cloud” or all or apart of a fab host computer system, which can allow for remote access ofthe wafer processing. The computer may enable remote access to thesystem to monitor current progress of fabrication operations, examine ahistory of past fabrication operations, examine trends or performancemetrics from a plurality of fabrication operations, to change parametersof current processing, to set processing steps to follow a currentprocessing, or to start a new process. In some examples, a remotecomputer (e.g. a server) can provide process recipes to a system over anetwork, which may include a local network or the Internet. The remotecomputer may include a user interface that enables entry or programmingof parameters and/or settings, which are then communicated to the systemfrom the remote computer. In some examples, the system controller 550receives instructions in the form of data, which specify parameters foreach of the processing steps to be performed during one or moreoperations. It should be understood that the parameters may be specificto the type of process to be performed and the type of tool that thesystem controller 550 is configured to interface with or control. Thusas described above, the system controller 550 may be distributed, suchas by including one or more discrete controllers that are networkedtogether and working towards a common purpose, such as the processes andcontrols described herein. An example of a distributed controller forsuch purposes would be one or more integrated circuits on a chamber incommunication with one or more integrated circuits located remotely(such as at the platform level or as part of a remote computer) thatcombine to control a process on the chamber.

Without limitation, example systems may include a plasma etch chamber ormodule, a deposition chamber or module, a spin-rinse chamber or module,a metal plating chamber or module, a clean chamber or module, a beveledge etch chamber or module, a physical vapor deposition (PVD) chamberor module, a chemical vapor deposition (CVD) chamber or module, an ALDchamber or module, an atomic layer etch (ALE) chamber or module, an ionimplantation chamber or module, a track chamber or module, and any othersemiconductor processing systems that may be associated or used in thefabrication and/or manufacturing of semiconductor wafers.

As noted above, depending on the process step or steps to be performedby the tool, the system controller 550 might communicate with one ormore of other tool circuits or modules, other tool components, clustertools, other tool interfaces, adjacent tools, neighboring tools, toolslocated throughout a factory, a main computer, another controller, ortools used in material transport that bring containers of wafers to andfrom tool locations and/or load ports in a semiconductor manufacturingfactory.

An appropriate apparatus for performing the methods disclosed herein isfurther discussed and described in U.S. patent application Ser. No.13/084,399 (now U.S. Pat. No. 8,728,956), filed Apr. 11, 2011, andtitled “PLASMA ACTIVATED CONFORMAL FILM DEPOSITION”; and Ser. No.13/084,305, filed Apr. 11, 2011, and titled “SILICON NITRIDE FILMS ANDMETHODS,” each of which is incorporated herein in its entireties.

The apparatus/process described herein may be used in conjunction withlithographic patterning tools or processes, for example, for thefabrication or manufacture of semiconductor devices, displays, LEDs,photovoltaic panels and the like. Typically, though not necessarily,such tools/processes will be used or conducted together in a commonfabrication facility. Lithographic patterning of a film typicallyincludes some or all of the following operations, each operation enabledwith a number of possible tools: (1) application of photoresist on aworkpiece, i.e., substrate, using a spin-on or spray-on tool; (2) curingof photoresist using a hot plate or furnace or UV curing tool; (3)exposing the photoresist to visible or UV or x-ray light with a toolsuch as a wafer stepper; (4) developing the resist so as to selectivelyremove resist and thereby pattern it using a tool such as a wet bench;(5) transferring the resist pattern into an underlying film or workpieceby using a dry or plasma-assisted etching tool; and (6) removing theresist using a tool such as an RF or microwave plasma resist stripper.

EXPERIMENTAL

An experiment as conducted for measuring wet etch rate of siliconnitride material deposited by thermal atomic layer deposition. A 20 Åsilicon nitride film was deposited on a first substrate using repeateddeposition cycles at a deposition rate of 0.37 Å/cycle, each depositioncycle including: disilane dose, purge, nitrogen plasma dose, purge. Therefractive index was measured to be 1.75. The wet etch rate of thissilicon nitride film was about 1000 Å/min in 100:1 dilute hydrofluoricacid.

A 20 Å silicon nitride film was deposited on a second substrate usingrepeated deposition cycles at a deposition rate of 0.1 Å/cycle, eachdeposition cycle including: SiBr₄ dose, purge, nitrogen plasma dose,purge, N₂/He treatment at 250° C. The refractive index was measured tobe 1.95. The wet etch rate of this silicon nitride film was about 15Å/min in 100:1 dilute hydrofluoric acid.

An FTIR spectrum was obtained for the silicon nitride film. The FTIRspectrum is shown in FIG. 6. Peak 601 shows the absorbance peak forSi—N—Si bonds, peak 603 shows the absorbance peak for Si₂N—H bonds, peak605 shows the absorbance peak for N—H₂ bonds, peak 607 shows theabsorbance peak for Si—H bonds, and peak 609 shows the absorbance peakfor Si₂N—H bonds. As shown in FIG. 6, the treated silicon nitride filmhas low N—H content, and hydrogen content in the film is very low.

CONCLUSION

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, it will be apparent thatcertain changes and modifications may be practiced within the scope ofthe appended claims. It should be noted that there are many alternativeways of implementing the processes, systems, and apparatus of thepresent embodiments. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the embodiments arenot to be limited to the details given herein.

1. A method of processing substrates, the method comprising: providing asubstrate to a chamber; depositing a conformal silicon nitride film overthe substrate at a first temperature using a deposition cycle, eachdeposition cycle comprising: exposing the substrate to a chlorine-freesilicon precursor under conditions allowing the chlorine-free siliconprecursor to adsorb onto a surface of the substrate, thereby forming anadsorbed layer of the chlorine-free silicon precursor, and exposing theadsorbed layer of the chlorine-free silicon precursor to anitrogen-containing reactant to form a silicon nitride film over thesubstrate using a plasma-free thermal reaction; and treating the siliconnitride film to form a treated silicon nitride film by exposing thesilicon nitride film to a treatment gas and igniting a plasma at asecond temperature less than 100° C. to form the treated silicon nitridefilm, wherein the silicon nitride film is deposited over one or moreexposed layers of chalcogenide material.
 2. The method of claim 1,wherein the first temperature is between 100° C. and 250° C.
 3. Themethod of claim 1, wherein the second temperature is between 25° C. and100° C.
 4. The method of claim 1, wherein the second temperature isbetween 50° C. and 100° C.
 5. The method of claim 1, wherein wet etchrate of the treated silicon nitride film in 100:1 hydrofluoric acid isless than about 30 Å/minute.
 6. The method of claim 1, wherein treatingthe silicon nitride film reduces wet etch rate of the silicon nitridefilm in 100:1 hydrofluoric acid by at least 90%.
 7. The method of claim1, wherein the treatment gas is selected from the group consisting ofnitrogen and helium.
 8. The method of claim 1, further comprisingrepeating the deposition cycle to deposit the conformal silicon nitridefilm.
 9. The method of claim 8, wherein treating the silicon nitridefilm is performed after every deposition cycle.
 10. The method of claim8, wherein treating the silicon nitride film is performed every ndeposition cycles, and n is an integer greater than
 2. 11. The method ofclaim 1, wherein the treated silicon nitride film has less than 5%hydrogen in atomic content.
 12. The method of claim 1, wherein theconformal silicon nitride film is deposited to a thickness less thanabout 50 Å. 13-14. (canceled)
 15. The method of claim 1, wherein thetreated silicon nitride film has a density of at least about 2.4 g/cc.16. The method of claim 1, wherein the treating the silicon nitride filmreduces N—H content of the silicon nitride film as measured by FTIR ascompared to the silicon nitride film prior to the treating.
 17. Themethod of claim 1, wherein treating the silicon nitride film isperformed for a duration between about 1 second and about 10 seconds.18. The method of claim 1, wherein the chlorine-free silicon precursorselected from the group consisting of iodine-containing siliconprecursors, bromine containing silicon precursors, andiodine-and-bromine-containing silicon precursors.
 19. The method ofclaim 1, wherein the chlorine-free silicon precursor is selected fromthe group consisting of compounds having a chemical formula ofSi_(x)Br_(y)I_(z), where x=1, y is an integer between and including 1and 4, and y+z=4; and compounds having a chemical formula ofSi_(x)Br_(y)I_(z), where x=2, y is an integer between and including 1and 6, and y+z=6.
 20. The method of claim 19, wherein the chlorine-freesilicon precursor is selected from the group consisting oftetrabromosilane (SiBr₄), SiBr₃I, SiBr₂I₂, SiBrI₃, hexabromodisilane(Si₂Br₆), Si₂Br₅I, Si₂Br₄I₂, Si₂Br₃I₃, Si₂Br₂I₄, Si₂BrI₅, andcombinations thereof.
 21. A method of processing substrates, the methodcomprising: providing a substrate to a chamber; depositing a conformalsilicon nitride film over the substrate at a first temperature by:exposing the substrate to a chlorine-free silicon precursor underconditions allowing the chlorine-free silicon precursor to adsorb onto asurface of the substrate, thereby forming an adsorbed layer of thechlorine-free silicon precursor, and exposing the adsorbed layer of thechlorine-free silicon precursor to a nitrogen-containing reactant toform a silicon nitride film over the substrate using a plasma-freethermal reaction; and treating the silicon nitride film by exposing thesilicon nitride film to a treatment gas and igniting a plasma at asecond temperature less than 100° C. to form a treated silicon nitridefilm, wherein the silicon nitride film is deposited over a memory stackcomprising germanium, antimony, and tellurium.